The research topics on appliance detection problem can be classified into two categories based on the difference of hardware and software deployment. One uses single sensor to monitor the power outlet or multiple sensors to measure the electrical information of individual appliance. Special technical expertise is usually required for single sensor deployment, and multiple sensor installation and maintenance incur high cost. The other utilizes data mining techniques to disaggregate overall consumption data into individual device level and associate different levels of consumption to existing appliance feature (signature) database. The consumption data is typically sampled at high frequency. In addition, the prior knowledge about appliance consumption (signature) is difficult to obtain.